I've found lots of info on decrypting PDF files, but none on encrypting them. What tool can do this for me?
Edit: There are two good answers below, but in my specific case the PDF was a scan, not a document that I'd created.
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pdftk. From its
Encrypt a PDF using 128-Bit Strength (the Default) and Withhold All Permissions (the Default)
$ pdftk [mydoc].pdf output [mydoc.128].pdf owner_pw [foopass]
Same as Above, Except a Password is Required to Open the PDF
$ pdftk [mydoc].pdf output [mydoc.128].pdf owner_pw [foo] user_pw [baz]
Same as Above, Except Printing is Allowed (after the PDF is Open)
$ pdftk [mydoc].pdf output [mydoc.128].pdf owner_pw [foo] user_pw [baz] allow printing
pdftk has a lot of other uses as well and is worth installing if one works extensively with PDF files. To quote from the write-up in Synaptic:
If PDF is electronic paper, then pdftk is an electronic stapler-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a simple tool for doing everyday things with PDF documents. Keep one in the top drawer of your desktop and use it to:
- Merge PDF documents
- Split PDF pages into a new document
- Decrypt input as necessary (password required)
- Encrypt output as desired
- Fill PDF Forms with FDF Data and/or Flatten Forms
- Apply a Background Watermark
- Report PDF on metrics, including metadata and bookmarks
- Update PDF Metadata
- Attach Files to PDF Pages or the PDF Document
- Unpack PDF Attachments
- Burst a PDF document into single pages
- Uncompress and re-compress page streams
- Repair corrupted PDF (where possible)
qpdf can encrypt and decrypt pdfs. And linearize them, too.
qpdf --password='·······' --decrypt input.pdf output.pdf
qpdf --encrypt userpwd ownerpwd 256 -- input.pdf output.pdf
Link to qpdf online Manual
PDF Chain is an awesome tool for this. It is a GUI for pdftk
One possible solution is to use jpdf Tweak.
Master PDF Editor is a very good GUI for editing pdf also can encrypt. It also uses latest PDF standard. Used PDF Chain and Master PDF editor, both to encrypt a pdf, With PDF Chain the PDF outputed was larger and lost bookmarks, was almost double the size.